Zhenzhong Hu<zhenzhong.hu@mun.ca>, Fran M. Kerton*<fkerton@mun.ca> Department of Chemistry, Memorial University of Newfoundland,

St. John’s, NL, Canada, A1B 3X7

Efficient aerobic oxidation of alcohols using CuBrEfficient aerobic oxidation of alcohols using CuBr22 and and a a series of series of α-α- pyridyl-imine terminated pyridyl-imine terminated

polydimethylsiloxane ligandspolydimethylsiloxane ligands

IntroductionIntroductionFrom the point of view of Green Chemistry, polymer-

based catalysts are very environmentally friendly. These

catalysts can be used and recycled in green solvents

such as liquid polymers and supercritical carbon dioxide.

They can also be very selective.

In our recent studies, a series of α- pyridyl-imine

terminated polydimethylsiloxane ligands have been

synthesized and characterized. It is interesting that these

carbon dioxide miscible ligands form metallocyclic

complexes when coordinated with copper(I) salt.

Meanwhile, they provide perfect binding sites for copper

(II) ions which then work as catalysts for more efficient

aerobic oxidations of primary and secondary alcohols.

Cloud point data for L1 ( ) and [Cu(L2)](PF6) (▲) in carbon dioxide. L2 is miscible in liquid CO2. [Cu(L1)](PF6) is insoluble at Ts and Ps studied.

[Cu(CH3CN)4](PF6) + L [Cu(L)](PF6)

Aerobic oxidation of selected alcohols with Aerobic oxidation of selected alcohols with in situ made TEMPO/[Cu]/L1 systemin situ made TEMPO/[Cu]/L1 system

5 mol% CuBr2, 2.5 mol% L15 mol% TEMPO, 5 mol% t-BuOK

CH3CN/H2O (2:1), air, 25 ºCR1 R2

OH

R1 R2

O

[a] GC conversion, selectivity > 99%; [b] Reaction temperature = 45 oC, using compressed air; [c] Reaction time = 48 h

SummarySummary• α-Pyridyl-imine terminated PDMS compounds have

been prepared and characterised.• Coordination chemistry with Cu(I) shows the formation

of [1+1] metallocycles.

• The TEMPO/[CuBr2]/L1 catalytic system is very

effective for the aerobic oxidation of alcohols.• Future studies will involve the study of catalytic

reaction mechanism and the recycling of the catalyst.• Attempts will also be made to obtain further evidence

for the structures of these metallocyclic polymers.

Acknowledgements; Acknowledgements; Prof. Christopher M. Kozak; Green Chemistry and Catalysis Group; Dr. Celine Schneider ; C-CART (Brent, Linda & Julie); Chemistry Department, Memorial University

Coordination ChemistryCoordination Chemistry

• L2 titrated with Cu(I) reagent (L1 behaves similarly)

• MLCT band max. intensity reached at a ratio CM/CP= 1

• Metallocyclopolymer is characterised by NMR, FT-IR, GPC, CHN, MALDI-TOF MS

LigandLigandSynthesisSynthesis

Solubility in Supercritical COSolubility in Supercritical CO22